Internally coated tubular casing and process for the manufacture thereof

ABSTRACT

Disclosed is a packaging material, preferably a sausage casing, comprising a layer based on cellulose hydrate, having a coating on one surface, this coating comprising a mixture of chemically different compounds comprising, as the first major component thereof, a natural oil comprising a vegetable oil, a triglyceride mixture of saturated vegetable fatty acids having from about 4 to 14 carbon atoms in their carbon chain, or a mixture thereof, and as the second minor component thereof, a chemically modified starch, a partially saponified polyvinyl alcohol or a micro-crystalline cellulose. Also disclosed is a process for manufacturing such sausage casings.

BACKGROUND OF THE INVENTION

The present invention relates to tubular casings based on cellulosehydrate which carry on their inside surface a coating of a mixture ofchemically modified starch and natural oils which can be easily peeledoff from the filling mass. Furthermore, the present invention relates toa process for the manufacture of such tubular casings. Finally, thepresent invention relates to the use of such tubular casings as apackaging material, in particular as an artificial sausage casing whichcan be easily removed from the sausage mass.

Tubular cellulose hydrate casings, the inside of which is notpre-treated, have only a limited suitability for use as sausage casings,because, in the case of fresh sausage, the sausage mass adheres sofirmly to the casing that it is almost impossible to separate the casingfrom the sausage mass when required. In the case of long-keeping orsummer sausages, on the other hand, the adhesion is so slight that thecasing already detaches itself from the sausage mass during the dryingstep when the sausage is prepared. Because it detaches itself from thesausage mass when the summer sausage is dried, the casing does notshrink together with the sausage mass and thus becomes crumpled andunsightly, and such properties impede the sales of the sausage.

It has already been suggested to avoid these drawbacks by providing theinside of cellulose hydrate based casings with a layer comprisingchemical compounds which act as release agents, such as long-chainisocyanates, ethylene imines, chromium fatty acid complexes, silicones,perfluorinated chemical compounds, diketenes and the like.

Furthermore, artificial sausage casings for long-keeping sausages basedon cellulose hydrate are known which carry on their inside surface alayer comprising albuminous chemical compounds, in order to create asatisfactory adhesion between the sausage mass and the sausage casing.Such albuminous compounds are, e.g., chemically modified proteins,epichlorhydrin/polyamine polyamide resins, urea- ormelamine-formaldehyde resins, and the like.

These finishing processes for treating the inside surfaces of artificalsausage casings based on cellulose hydrate have the drawback, however,that they are very expensive, because in most cases specificmanufacturing conditions must be maintained for the chemical reactionbetween the cellulose hydrate and the chemical compounds from which thecoating is formed. Furthermore, the known finishing processes invariablyrequire the use of chemical compounds of complicated chemical structurewhich are relatively expensive.

Frequently, such treatments involve the risk that the cellulose hydrateforming the tubular casing is cross-linked in an undesirable anduncontrollable manner by the use of the above-mentioned chemicalcompounds, so that the sausage casing becomes brittle and breaks. Thus,holes may appear in the wall of the sausage casing when the casing isused in accordance with its purpose, e.g., shirred into a stick.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide improvedtubular casings.

Another object of the invention resides in providing improved tubularcasings especially fiber-reinforced cellulose hydrate casings, whichcarry on their inside surfaces a coating of chemical compounds which arenot linked by a chemical reaction to the cellulose hydrate forming thecasing, i.e., cross-linking of the cellulose hydrate molecules is ruledout, this coating causing a good release effect between the casing andthe filling mass and simultaneously providing for a good slip andplasticization of the casing.

It is also an object of the invention to provide a tubular casing to beused as a food pack, with the chemical compounds forming the coatingbeing toxicologically safe.

A specific object is the provision of an improved sausage casing.

It is also an object of the invention to provide a method for making theimproved tubular casings according to the invention.

In accomplishing the foregoing objects, there has been provided inaccordance with one aspect of the present invention a packagingmaterial, preferably in the form of a sausage casing, comprising a layerbased on cellulose hydrate, this layer having a coating on one surface,with the coating comprising a mixture of chemically different compoundscomprising, as the first, major component thereof a natural oilcomprising a vegetable oil, a triglyceride mixture of saturatedvegetable fatty acids having from about 4 to 14 carbon atoms in theircarbon chain, or a mixture thereof and, as the second minor componentthereof, a chemically modified starch, a partially saponified polyvinylalcohol or a micro-crystalline cellulose. Preferably, the mixtureforming the coating comprises between about 20 and 200 mg of the firstcomponent and between about 5 and 150 mg of the second component,calculated per square meter of the surface of the cellulose hydratelayer.

In accordance with another aspect of the present invention, there hasbeen provided a process for the preparation of the above-describedtubular casings comprising the steps of coating the inside of a tubularcasing based on cellulose hydrate with an aqueous liquid comprising fromabout 0.2 to 8 percent by weight, based on the total weight of theliquid, of a chemically modified starch, a micro-crystalline celluloseor a partially saponified polyvinyl alcohol, and from about 2 to 20percent by weight, based on the total weight of the liquid, of a naturaloil, evaporating the volatile components of the liquid, the quantity ofliquid applied being selected so that the coating formed on the surfaceof the tube after evaporation of the volatile components comprises amixture of chemical compounds comprising a total of from about 20 to 200mg of natural oil and a total of from about 5 to 150 mg of a chemicallymodified starch, a micro-crystalline cellulose, or a partiallysaponified polyvinyl alcohol, calculated per square meter of the surfaceof the tubular casing. Optionally, the aqueous liquid further comprisesa chemical emulsifier.

Further objects, features and advantages of the present invention willbecome apparent from the detailed description of preferred embodimentswhich follows.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The manufacture of tubular casings based on cellulose hydrate is knownand does not form a part of the present invention. Processes forproviding cellulose hydrate tubes with inside coatings are also knownand have been disclosed, e.g., in British Pat. No. 1,201,830, and inU.S. Pat. Nos. 2,901,358 and 3,378,379; therefore, such processes do notper se form a part of the present invention.

The coating on the inside surface of the tubular casing comprises amixture of chemical compounds based on natural oils and/or triglyceridemixtures of natural vegetable fatty acids with carbon chains ranging inlength from about 4 to 14 carbon atoms, and a second componentconstituting the minor part of the mixture, which comprises non-reactivehydrophilic, water-soluble or water-swellable chemically modified starchderivatives and/or micro-crystalline cellulose and/or partiallysaponified water-soluble polyvinyl alcohol, preferably high molecularweight polyvinyl alcohol.

The mixture forming the coating is comprised of from about 20 to 200 mgof the first component and from about 5 to 150 mg of the secondcomponent, calculated per square meter of the surface of the cellulosehydrate casing. Preferably, the coating contains between about 20 and200 mg of a vegetable oil and/or triglyceride mixtures of vegetablefatty acids with 4 to 14 carbon atoms. The starch derivatives form therelease agent component and the vegetable oils form the slip agentcomponent of the mixture of chemically different compounds whichtogether forms the coating. The result achieved by the present inventionis due to the synergistic effect caused by the inventive combination ofstarch derivatives and natural vegetable oils.

The following compounds may be used according to the present inventionas chemically modified starches: dextrines, dextranes, alkyl starchethers, carboxymethyl starch ethers, hydroxyalkyl starch ethers,especially methyl starch, ethyl starch, hydroxymethyl starch,hydroxypropyl starch, ethylmethyl starch, and carboxy methylhydroxyethyl starch. Within the above-mentioned quantitative ratio, anyof these starches, or a mixture of several of these starches, may form apart of the mixture from which the coating is formed.

In addition to vegetable oils and/or triglyceride mixtures of vegetablefatty acids with 4 to 14 carbon atoms, which forms the first component,the coating according to the present invention comprising a mixture ofchemically different substances may contain micro-crystalline celluloseas the second component. Calculated on its total weight, the firstcomponent of the mixture outweighs the second component.

The scope of the present invention also comprises an embodiment whereinthe mixture of chemically different substances forming the coatingcomprises, as the first component, vegetable oils and/or triglyceridemixtures of vegetable fatty acids with 4 to 14 carbon atoms, and, as thesecond component, a water-soluble polyvinyl alcohol, the first componentoutweighing the second component, calculated on the total weight of themixture.

Preferably, such polyvinyl alcohols contain at least about 88 percent,preferably from about 88 to 99 percent of free OH groups, i.e., OHgroups which are not esterified. The percentages refer to the totalnumber of OR groups present in the molecule, wherein R stands forhydrogen or an acid group. Polyvinyl alcohols with high molecularweights are preferred. The term "partially saponified polyvinylalcohols" refers to chemical compounds of the type described on page2776 of Roempp's "Chemie-Lexikon" (Chemical Dictionary), published byFranckh'sche Verlagshandlung, Stuttgart, 7th Edition, 1977, under theheading "Polyvinylalkohol".

If the chemical substances forming the coating are present in higherconcentrations, the effect is not increased, and it may even occur thatundesirable jelly or fat depositions form on the inside of the casing.

Natural oils which are particularly preferred are linseed oil, oliveoil, sunflower oil, and a triglyceride mixture of saturated vegetablefatty acids with a chain length of from about 4 to 12 carbon atoms,preferably from about 6 to 10 carbon atoms. The oil component of thecoating may also comprise a mixture of the above-mentioned preferrednatural oils.

Due to the manner in which it is prepared, the coating according to theinvention contains a quantity of a chemical emulsifier such that thedesirable qualities of the coating or of the tubular casing providedwith the internal coating are not affected. Emulsifiers of this typeare, e.g., ethoxylates or propoxylates of natural fatty acids, which areobtained, e.g., by saponification of natural oils, such as soybean oil,linseed oil, castor oil and the like, or monoesters or diesters ofnatural fatty acids with polyhydric alcohols, such as glycerol,pentaerithritol, sorbitol, mannitol and the like. Also there may be usedtoxicologically safe synthetic emulsifiers of the type which may belegally added to foodstuffs, such as alkyl or alkyl-aryl-sulfates orsulfonates.

The following is a description of the preparation of a tubular casingaccording to the present invention.

A tubular cellulose hydrate casing prepared in known manner is used asthe starting material. By means of one of the above-mentioned knownprocesses, e.g., a section of a given length, e.g. 350 m, of such atubular casing is continuously coated on its inside surface with anaqueous liquid comprising chemically modified starch and natural oils.The tube is then dried as described and may then be moistened with waterin a manner such that the finished tube has a water content in the rangefrom about 8 to 10 percent by weight, calculated on the total weight ofthe tube.

The aqueous liquid used for coating the inside of the cellulose hydratetube may be prepared as follows:

Between 2 and 80 g of chemically modified starch, e.g. carboxymethylstarch, is dissolved in 1 liter of water with agitation. A total of 2 to20 g of a chemical emulsifier, e.g. a reaction product of soybean fattyacid with 12 moles of ethylene oxide, is then added to the solution.Then a total of 20 to 200 g of a natural oil, e.g., sunflower oil, isadded to the solution and thoroughly emulsified by vigorous stirring.

The tube is dried at a temperature between about 90° and 120° C. Inorder to produce stable oil emulsions, between about 5 and 20 percent byweight of emulsifiers, preferably between about 9 and 12 percent byweight, based on the total weight of the oil present, are required.

Ethyoxylated soybean fatty acids (52.5% of linoleic acid, 33.5% of oleicacid, palmitic acid, linolenic acid, and arachidic acid, reacted with 12moles of ethylene oxide), ethoxylated castor oil acid (86% of castor oilacid, 9% of oleic acid, 2 to 3% of linoleic acid, 2% of stearic acid,reacted with 36 moles ethylene oxide), and ethoxylated oleic acids areparticularly advantageous emulsifiers.

If desired, the liquid containing the chemically modified starch and thenatural oils may be applied immediately before the tube is shirred intoa so-called stick, by means of known shirring processes and shirringapparatuses, for example by spraying the liquid through the hollowshirring mandrel into the interior of the tube which is being shirred.

Tubular casings produced by the present process which are used asartificial sausage casings for fresh sausage can be easily peeled fromthe sausage mass. No annoying rupture occurs, because the tubular casingwill not become brittle.

The tubular casings according to the present invention are particularlysuitable for sausages packed in so-called "peelable sausage casings";the casings of such sausages are mechanically removed from the sausagemass before the sausages are sold or before they are further processed.The ready detachability of the sausage casings according to the presentinvention from the sausage mass facilitates a smooth mechanical peelingof the tubular casings from the sausage mass, i.e., ruptures caused bythe adhesion of sausage mass or damage to the casing by mechanicalaction do not occur. By the presence of natural oils in the coating,after-treatment and further processing of the casings, e.g. shirring,are also facilitated.

If the tubular casings according to the present invention are wound upinto a roll, they do not stick during storage, a property, which is ofimportance for the subsequent shirring of the sausage casings. Sectionsof the casings can be easily opened during processing, which isessential if tubular casings of relatively large sizes are processedinto artificial sausage casings, because the sausage casings areprocessed with one end thereof tied. If the tubular casings according tothe present invention are to be further processed as artificial sausagecasings, it is of importance that the tubes be flexible and soft, forshirring into sticks, for tying, and for further processing of thecasings. The casing according to the present invention has theseproperties to a high degree.

If they are used as artificial sausage casings, the tubular casingsaccording to the present invention fill a gap in the market in that theyare particularly suitable for sausages destined for early consumption,e.g., for thick Frankfurters, finely minced pork sausages, coarse andfine mettwurst, and the like.

The coating on the inside of the tubular casing according to theinvention does not display the excessive release (lack of adhesion)effect of known hydrophobic layers, or the excessive adhesion of thecasing to the sausage mass of known albuminous inside coatings, but isan advantageous combination of release effect and adhesion.

The following examples are illustrative of the present invention.

EXAMPLE 1

(a) 12 g of carboxymethyl starch and 15 g of a reaction product ofsoybean fatty acid with 12 moles of ethylene oxide are dissolved, whileagitating, in 1 liter of water. Then 150 g of a triglyceride mixture ofsaturated vegetable fatty acids with 4 to 12 carbon atoms (e.g.,"Miglykol 812", marketed by Dynamit Nobel AG) is stirred into thesolution and carefully emulsified.

(b) The inside of a tubular cellulose hydrate casing is treated asfollows: The above described liquid is filled into a section of about350 m length of a cellulose hydrate tube of size 40 in a manner suchthat the entire quantity of the liquid is contained within a certainsection of the hollow space of the tube. Inside coating of the tube iseffected, e.g., in accordance with the process disclosed in British Pat.No. 1,201,830, the disclosure of which is hereby incorporated byreference.

The internally coated tube is then dried by passing it continuouslythrough a tunnel drier at a drying temperature between 90° and 120° C.After leaving the drier, the tube is moistened by spraying it with waterin a manner such that the finished sausage casing has a water content ofabout 8 to 10 percent by weight, based on the total weight of the tube.The tube is then wound onto a roll.

If the thus treated casing is collapsed and handled between thumb andforefinger of one hand, the adjacent inside surfaces of the tube may beeasily displaced relative to each other. Even after prolonged storage ofthe tube, the walls do not stick to each other. The tube may be shirredwithout difficulties and is not damaged by the shirring process. Thesticks produced by shirring can be processed without difficulties onconventional sausage filling machines. The artificial sausage casingsmay be easily peeled from the sausage or the sausage meat withouttearing or sticking to the sausage meat.

EXAMPLE 2

(a) 15 g of propoxylated starch and 1.0 g of a reaction product ofcastor oil with 36 moles of ethylene oxide are dissolved in 1 liter ofwater. Then 150 g of a triglyceride mixture of saturated vegetable fattyacids with 4 to 12 carbon atoms (e.g., "Miglykol 812", marketed byDynamit Nobel AG) is emulsified in the solution with thorough agitation.

(b) A cellulose hydrate tube of size 38, which is still in the gelstate, is provided with an inside coating as described in Example 1. Acellulose hydrate tube in the gel state is a cellulose hydrate tubewhich, without having previously been dried, has a water content ofabout 300 percent by weight, based on the total weight of the tube.

The resulting product is distinguished by its good processability in themanufacture of sausages and is characterized in that the artificialsausage casing can be easily peeled from the sausage mass when desired,without tearing of the tubular casing or adhesion of the sausage mass tothe sausage casing.

EXAMPLE 3

(a) The liquid used corresponds to that used in Example 1.

(b) This solution is also filled into an annular casing (round-shapedcellulose tube) of size 42 before the casing is introduced into thedrier and is then dried in a slightly inflated state at a speed of 10m/min. During shirring, the tube is moistened so that a water content of16 percent results. If the tube is filled with coarse mettwurst meat, nodamage occurs. The casing thus produced can be easily peeled from thesausage mass.

EXAMPLE 4

(a) 20 g of a reaction product of soybean fatty acid with 12 moles ofethylene oxide is dissolved in 1 liter of water while vigorouslystirring. Then 120 g of sunflower oil are added to the solution withvigorous agitation and thoroughly emulsified in the solution.

(b) The resulting solution (a) is further processed as described inExample 1.

EXAMPLE 5

Example 4 is repeated except that olive oil is used instead of sunfloweroil.

EXAMPLE 6

Example 4 is repeated except that rape oil is used instead of sunfloweroil.

EXAMPLE 7

Example 4 is repeated except that palm oil is used instead of sunfloweroil.

EXAMPLE 8

Example 4 is repeated except that coconut oil is used instead ofsunflower oil.

EXAMPLE 9

Example 4 is repeated except that linseed oil is used instead ofsunflower oil.

EXAMPLE 10

A liquid corresponding to liquid (a) of Example 4 is used for coatingthe inside of a cellulose hydrate tube. The solution is filled into acellulose hydrate tube in the gel state (size 18) and further processedas described in Example 1. Then the tube is shirred to form a stick. Astick obtained from the tube prepared as described in this example isparticularly suitable for the manufacture of sausages casings which mustbe capable of being easily and rapidly peeled from the sausage mass.

EXAMPLE 11

Example 1 is repeated except that the treating liquid is prepared asfollows:

(a) 15 g of polyvinyl alcohol with a saponification degree of 88% (e.g.,"Mowiol N 30-88", marketed by Hoechst AG), and 15 g of a reactionproduct of soybean fatty acid with 12 moles of ethylene oxide aredissolved, with agitation, in 1 liter of water. 160 g of olive oil isadded to the solution and carefully emulsified.

(b) The inside surface of the tube is treated as described in Example 1.

EXAMPLE 12

Example 1 is repeated except that the treating liquid is prepared asfollows:

18 g of micro-crystalline cellulose ("Avicell", marketed by Rettenmeyer)and 16 g of polyoxy ethylene sorbitan-monooleate ("Tween 80", marketedby Atlas Chemie GmbH) are dissolved in 1 liter of water while stirring.160 g of olive oil are thoroughly emulsified in this solution byvigorous stirring.

What is claimed is:
 1. A packaging material, comprising a layer based oncellulose hydrate, said layer having a coating on one surface, saidcoating comprising a mixture of chemically different compoundscomprising, as the first, major component thereof between about 20 and200 mg/m² of a natural oil comprising a vegetable oil, a triglyceridemixture of saturated vegetable fatty acids having from about 4 to 14carbon atoms in their carbon chain, or a mixture thereof and, as thesecond, minor component thereof, between about 5 and 150 mg/m² of achemically modified starch, a partially saponified polyvinyl alcohol ora microcrystalline cellulose.
 2. A packaging material according to claim1, wherein the mixture of chemical compounds forming the coatingcomprises a natural oil and a modified starch derivative selected fromthe group comprising a dextrine, a dextrane, an alkyl starch ether, acarboxymethyl starch and a hydroxyalkyl starch ether.
 3. A packagingmaterial according to claim 2, wherein the starch ether comprises methylstarch, ethyl starch, hydroxymethyl starch, hydroxy propyl starch,ethylmethyl starch, or carboxymethyl hydroxyethyl starch.
 4. A packagingmaterial according to claim 1, wherein the second minor component of themixture comprises a partially saponified polyvinyl alcohol.
 5. Apackaging material according to claim 1, wherein the natural vegetableoil is selected from the group comprising olive oil, rape oil, palm oil,coconut oil, linseed oil, sunflower oil, or a triglyceride mixture ofsaturated vegetable fatty acids having from about 4 to 14 carbon atomsin their carbon chain.
 6. A packaging material according to claim 1,wherein the mixture of compounds forming the coating comprises saidnatural oil and a mixture of chemically different, chemically-modifiedstarches.
 7. A packaging material according to claim 1, wherein themixture of chemically different compounds forming the coating comprisesa mixture of chemically different natural oils selected from the groupcomprising olive oil, rape oil, palm oil, coconut oil, linseed oil,sunflower oil, or a triglyceride mixture of saturated vegetable fattyacids having from about 4 to 14 carbon atoms in their carbon chain.
 8. Apackaging material according to claim 1, wherein the coating has anoverall content of from about 5 to 150 mg of a chemically modifiedstarch and an overall content of from about 20 to 200 mg of said oil orof a triglyceride mixture of saturated vegetable fatty acids having fromabout 4 to 14 carbon atoms in their carbon chain, or of a mixturethereof, calculated per square meter of the surface of said layer.
 9. Apackaging material according to claim 1, in the form of a tubularcasing.
 10. A sausage product, comprising a sausage filling andsurrounding said filling, a casing as defined by claim
 9. 11. A processfor the preparation of a tubular casing, comprising the steps of coatingthe inside of a tubular casing based on cellulose hydrate with anaqueous liquid comprising from about 0.2 to 8 percent by weight, basedon the total weight of the liquid, of a chemically modified starch, amicro-crystalline cellulose, or a partially saponified polyvinylalcohol, and from about 2 to 20 percent by weight, based on the totalweight of the liquid, of a natural oil, evaporating the volatilecomponents of the liquid, the quantity of liquid applied being selectedso that the coating formed on the surface of the tube after evaporationof the volatile components comprises a mixture of chemical compoundscomprising a total of from about 20 to 200 mg of natural oil and a totalof from about 5 to 150 mg of a chemically modified starch, amicro-crystalline cellulose, or a partially saponified polyvinylalcohol, calculated per square meter of the surface of the tubularcasing.
 12. A process according to claim 11, wherein said aqueous liquidfurther comprises a chemical emulsifier.
 13. A process according toclaim 11, wherein the liquid comprises an aqueous solution of achemically modified starch which comprises a natural oil selected fromthe group of triglycerides comprising olive oil, rape oil, palm oil,coconut oil, linseed oil, sunflower oil, and a triglyceride mixture ofsaturated fatty acids having from about 4 to 14 carbon atoms in theircarbon chain.
 14. A process according to claim 11, wherein the aqueousliquid containing the chemical compounds forming the coating comprisesfrom about 0.2 to 2 percent by weight, calculated on the total weight,of a chemical emulsifier selected from the group consisting of anethyoxylate or propoxylate of a natural fatty acid, a monoester ordiester of a natural fatty acid with an aliphatic polyalcohol, an alkyl-or alkyl-aryl-sulfonate, and an alkyl- or alkyl-aryl-sulfate.